public class ceshi {
    public static void main(String[] args) {
        int [] arr =new int[10];

        for (int i = 0; i <5 ; i++) {
            arr[i] = i;
        }

        int [] arr2=new int[10];

        int usesize=0;

        for (int i = 0; i <arr.length ; i++) {      //arr{0,1,2,3,4,0,0,0,0,0},arr.length是10,arr前5个是有效数字，后五个是无效数字
            arr2[i]=arr[i];                         //arr2[0]=0.arr2[1]=1,arr2[2]=2,arr2[3]=3,arr2[4]=4,arr2[5]=?,arr2[6]=?
            usesize++;                              //usesize++到5以后，还会增加吗
        }

    }
}
